1. Field of the Invention
The present invention relates to a drive tool, and more particularly to a unidirectional drive tool mechanism.
2. Description of the Prior Art
Typical unidirectional drive tool mechanisms comprise a cylindrical housing including a number of recesses formed in the inner peripheral surface thereof for receiving a number of rods therein and including a shaft rotatably engaged therein for engaging with the rods. A number of springs are engaged in the recesses and engaged with the rods so as to bias the rods to engage with one end of the recesses and so as to allow the housing to drive the shaft unidirectionally. Several such typical unidirectional drive tool mechanisms are disclosed in U.S. Pat. No. 1,644,079 to O'Neill; U.S. Pat. No. 1,748,218 to Groves; U.S. Pat. No. 1,904,621 to Kounovsky; U.S. Pat. No. 1,907,584 to Richards; U.S. Pat. No. 3,590,667 to Berglein; U.S. Pat. No. 4,051,935 to Nakayama; U.S. Pat. No. 4,603,606 to Headen; and U.S. Pat. No. 4,873,898 to Chern. However, the drive tools each includes a single rod engaged in each of the recesses only. Some times, the rod may not be effectively engaged with the shaft such that the housing may not effectively and unidirectionally drive the shaft.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages of the conventional unidirectional drive tool mechanisms.